Once you get the hang of ascending with a figure 8, it’s not that bad, even on free hangs. The illustration Hank uploaded shows the system using a round 8. An advantage of a square 8 is that one corner of it will settle on your carabiner, so it is more stable. On vertical rope I also use a doubled 20 foot accessory cord as combination backup and foot loop. Since you will be using the 8 on your harness, your foot loop will have to be rigged above. As you stand up in the foot loop, pull up on the rope. Then move your hand back down below your hip as you come to rest on your harness. Move your foot loop ascender higher, stand up in the foot loop, etc. Once you get the rythm down, it can be a pretty efficient system. The only time I wouldn’t want to do it is on very long ascents — the weight of a lot of rope hanging below you will make it difficult to pull up and through your 8.
As Julien pointed out, switching from ascending to descending or visa versa is very quick, making it ideal if you need to get down/up to someone quickly, then reverse. The long cord comes in handy for other things as well — cordelette, raising systems, releasable bowlines for rope retrieval, etc.
Rich